Cryogenian Period 850 to 635 mya

Summary

The Cryogenian Period derives its name from
the Greek word cryos meaning cold and genesis meaning birth.

The greatest ice age
in history probably occurred during this period. This so-called ‘snowball
earth’ might have involved the whole Earth, although this is not yet
established.

Earth 700 mya

Continents 700 mya

We have little idea where the continents
had been for the first 4 billion years of Earth’s history, but from about 700
mya we can begin to draw maps of where we think they were, based on the
magnetic fields frozen into them as volcanic larva cooled into rock. Here is
the first of our reconstructions.